Variable speed electric motor



Feb 13 1951 l `c. H. vsPARKLlN 2,541,120

' VARIABLE SPEED ELECTRIC MOTOR Y Filed Oct. 31, 1946 v 2 Sheets-Sheet l m k s QQ Y b, mi: P@

" Feb' 13 .1951* M 'l H.-sPARK| |N j j 12,541,120

Y' 5 VRIALE SPEED -ELECTRIC MOTOR',

Filed 0cm` y31. i946 U @Q7/g Patented Feb. 13, 1951 VARIABLE SPEED ELECTRIC MOTOR Charles Harold Sparklin, Chicago, Ill., assigner to Birtman Electric Company, a corporation of Illinok Application October 31, 1948, Serial No. 707,014

1 claim. l

This invention relates to a motor, particularly a motor having a speed control or a drive shaft separate from the motor shaft, or both, and relates especially to such a motor for use in food mixers or the like. The invention also relates to an improved speed control means.

Applicant has invented a new motor construction having speed control apparatus wherein at least a portion of the speed control means is mounted on a section of the casing and its speed control means may be mounted and dismounted as a unit. The motor also preferably includes various drive shafts or power connections, or a combination of these, mounted on another section of the casing so as to be also mountable and dismountable as a unit. This construction enables the motor and its various. controls and power takeoff means to be assembled in more compact form and makes the entire construction cheaper to build and easier to service. The invention also includes improvements in this speed control means itself.

The invention will be described as related to the embodiment set out in the accompanying drawings. Of the drawings Fig. 1 is a longitudinal vertical section taken through the motorr assembly along the line I-I of Fig. 2; Fig.,2 is a horizontal section taken along line 2-2vof 1Fig. 1; Fig. 3 is a section taken along line 3-3 of Fig. 1; and Fig. 4 is a section taken along line 4-4 of Fig. 1.

'I'he embodiment shown in the drawings is a food mixer motor comprising an armature I0, a surrounding field coil; II, a commutator I2, a motor shaft I3 upon which the armature and commutator are mounted. a main casing I4 surrounding the motor, avflrst casing section I5 at the front of the motor assembly, and a second casing section I6 at the rear of the motor assembly. The second casing section is rotatably mounted on a pedestal I 1 by means of a hinge pin'i.

The front endloi the motor shaft I 3 extends through a wall I9 separating the main casing from the first casing section I5. The motor shaft is held in a bearing 2li in this wall and the end of the shaft extending into the ilrst casing section I5 is formed as a worm gear 2|.

The worm gear 2I engages a horizontal gear wheel 22 keyed to a second worm gear 2l held in vertical position between a bottom bearing 24 tools may be inserted in the openings formed and engage either the bottom or top ends of the worm gear 23. As shown in Fig. 1 the bottom end of the worm gear 23 is connected to an agitator 2l having a beater portion 21. The top end of the worm gear is formed with a notch 28 to which tools such as juice extractors may be attached.

The second worm gear 23 engages a second gear wheel 29 arranged vertically and transverse to the motor assembly. This second gear wheel 29 is concentric with a socket 30 that is mounted on the wall I9 by means of a rear portion 3i extending through the wall until held in place by a boss 32 on the other side of the wall I9. The front of the socket 30 communicates with an opening at the front of the first casing section II, through which the shafts of power tools may be inserted to engage the slot 33 in a smaller shaft 10.

From` the above description it can be seen that the second worm gear 23 and attached gear wheel 22 are mounted on the first casing section I! and that the second gear wheel 29 and socket 90 are mounted on the wall I9. The wall I9 is separable from the motor casing I4 and is held in place by a plurality of bolts 34. The first casing section I5 is held in place by a plurality of bolts 35 having their heads in recesses 36 at the front of the first casing section I5. This casing section is also provided with a handle 31 on its top surface.

At the rear of the motor casing I4 there is located a wall 38 through which the other end of the motor shaft I3 extends, with this end being held in abearing 39. This wall is made integral with .the motor casing. I4, although it may be made separable if desired. The rear of the motor casing I4 contains thickenedportions 4II in which are mounted the motor brushes 4I.

The speed control means for the motor is mounted within the second casing section I9. The speed governor comprises two parallel plates 42 mounted for rotation on the rear end of the shaft I3, vwith the plates held in spaced-apart relationship. On the back oi' the inner plate 42 there is mounted a plurality of radial blades 1I that extend beyond the periphery kof the inner plate. These blades actas a fan and set up a circulation of air through the motor when the motor is in operation. The air enters spaced holes 'I2 at the opposite end of the motor casing I4 and is drawn around the motor, through openings 14 in the wall Il, around the fan. and out rear openings 'I5 in the casing section I6. y

Between thc/rotatable plates 42 are located a pair of centrifugally responsive arms 49 hingedly mounted at one end of each arm and arranged to be swung outwardly by centrifugal forces acting on the arms. These arms press against bell cranks 44 hingedly mounted on fulcrums 45,. The other end of each bell crank 44 bears against one arm of a second bell crank 46 arranged at right angles to the rotatable plates 42. The other arms of these bell cranks 46 extend toward the motor shaft I3 and bear against a rotatable thimble 41 mounted on the end of the shaft I3. Thus, by increasing rotation of the motor armature the thimble 41 is moved farther out from the rotatable plates 42, and this distance is dependent upon the speed of rotation of the motor.

In order to limit the speed to any predetermined value there are provided two contact arms 4I and 49, arranged substantially parallel to each other and transverse rto the motor shaft Il. These contact arms are mounted on short arms 11 hingedly mounted on the second casing section Il as by a hinge pinA 50. The other ends of the contact arms carry electrical contacts 9| The thimblel 41 extends through an opening ll in the nearer contact arm 58 and presses against a button 94 on the farther contact arm 49. The nearer short arm 11 has an extended portion 95 engaging a groove 69 in a vertical threaded bolt Il extending through the top of the casing section I6. The top ofl this bolt is provided with a cap 59 that may be grasped by the fingers in order to rotate the bolt 99. The contact points 9i against both contact arms 43 and 49. Thus the points li are held in contact until the speed of rotation causes the thimble 41 to move the arm 49 away from arm 49 against the urging of spring 94.

' are normally held in contact by first spring 90 extending around the hinge pin 59 and bearing` This breaks the electrical connection to the A motor, and the speed slows down until the points Il again come in contact. The speed may be.

varied by turning the cap Il to move the contact arms 49 and 49 toward and away from the motor shaft. In a typical installation the speed range or the speed control is approximately 6 to 1. By providing a second spring 4| extending between the rear of the casing section I9 and the rear portion of the contact arm 49 this speed range may be almost doubled. This type speed governor. its construction, and operation are shown in r greater detail in my co-pending application serial No. 580,114, med February sa, 1945, now Patent No. 2,532,345.

The contact arms 4l and 4l are preferably made of aluminum, copper, brass or other heatconducting metal. The contact points Il are each mounted directly on an arm while each arm is insulated at its base by blocks of insulation 16.

The contact arms may or may not be provided v,with spaced holes to improve the cooling effect of the cooling air.

'rse cooling au 'that is circulated through the' ilu motor by tan blades 1I is directed across the contact arms 4l and. and the contact points Il. This may be accomplished by locating the exit openings 19 adjacent the contact arms, by properly shaping the casing, by providing baiiies. or by any combination of these. As illustrated in Figs. 1 and 2 the concentration of air is accomplished both by shaping the casing section I9 and by locating the air exit holes 1l adjacent the contact arms and points.

In the ordinary installations of the speed governor a condenser is provided across the contact points to reduce sparking, and a second condnser is also preferably provided in the electric l e The casing for the motor and for the speed governor may be made of any material, but is preferably a light weight metal such as aluminum.

Ag can be seen from the above description, the contact arms 48 and 49, the springs 9| and Il, the threaded bolt Il, and the cap Il are mounted on the second casing section i9, and the assembly may be removed as a unit. The second casing section is normally held in position by means of a plurality of bolts Il.

The button 94 that is mounted on contact arm 49 is insulated from this arm, and the spring Il is also insulated from arm 44.

Having described my invention as related to the embodiment set' out in the accompanying drawings, it is my intention that the invention be not limited by any of the details of descriptionunless otherwise specified, but rather be construed broadly within its spirit and scope as set out in the accompanying claim.

I claim:

In a variable speed motor construction including a movable make and break switch for controlling the speed thereof, positioning means for the switch, a casing surrounding said construction, and a set of gears operated by said motor: a casing section forming a part of one end of said casing and removable from the remainder thereof' including that portion surrounding the motor, said switch and said positioning means being mounted within said second casing section to form a removable unit therewith.

CHARLES HAROLD SPARKLIN.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,434 640 Wencker Nov. 7, 1922 1,965,669 Robb July 10, 1934 2,099,050 Chamberlain Nov. 16, 1937 2,103,589 Lee Dec. 28, 1937 2,143,921 Lewis Jan. 17, 1939 2,187,272 Kochner Jan. 16, 1940 2.188.559 Taylor Jan. 30. 1940 2,241,528 Strauss et al May 13, 1941 2,292,567 Jordan Aug. 11, 1942 2,353,314 Lee July 1i, 1944 2,381,914 Lear et al Aug. 14, 1945 

